In the field of an electrophotographic type image forming apparatus, it is known that elements such as a photosensitive drum and/or a developing roller as a rotatable member contributable to image formation are unified into a cartridge, which is detachably mountable to the main assembly of the image forming apparatus (main assembly).
As one of such a cartridge detachably mountable to the Image forming apparatus, there is known a toner cartridge which is exchangeable and which does not include the photosensitive drum or the developing roller, the toner cartridge containing toner (developer) which is to be consumed with the Image formation.
With such a structure, the toner (developer) is discharged through the discharge opening from the toner cartridges into a developing device including the developing roller and so on. In addition, in order to prevent the toner from leaking out through the discharge opening, an open/close member such as a shutter for opening and closing the discharge opening is provided.
Japanese Laid-open Patent Application Hei 7-199623, for example discloses a structure in which when a cylindrical toner cartridge (developer supply container) is mounted to the main assembly of the image forming apparatus, the toner cartridge is rotated by which the shutter is opened.